Heat exchanging tube



Nov. 3, 1931. F. B. ALLEN 1,829,731

HEAT EXCHANGING TUBE Filed April 9, 1926 l/l l I Patented Nov.' 3, 1931UNITED STATES PATENT OFFICE FRANK B. ALLEN, OF LOWER MERION TOWNSHIP,MONTGOMERY COUNTY, PENNSYIr' VANIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TOTHE ALLEN-SHERMAN-HOFF COMI- IPANY, OF PHILADELPHIA, PENNSYLVANIA., A.CORPORATION OF PENNSYLVANIA HEAT EXCHANGING TUBE Application filed April9, 1926. Serial No. 100,895.

This invention relates to the art of exchanging/heat and is moreparticularly concerned with heat exchange tubes for furnaces.

It also relates to means for strengthening and/or longitudinallysupporting and /or 1ncreasingthe heat absorbing surfaces of heatexchange tubes while automatically maintaining the tube substantiallyfree of, and of v preventing the accumulation on the top of the tubes ofincombustible solids carried by the heated gases to which the tubes areexosed.

p Various objects and-advantages of my invention will appear vin thisspecification which includes a description of certain structures andapparatus embodying my invention. In the drawings accompanying andformz'ing a part of this specification- Fig. l is a vertical,longitudinal sectlon through a furnace equipped with one form ofapparatus embodying this invention parts being broken away;

Fig. 2 is an enlarged transverse sectional view of the. apparatus ofFig. l;

Fig. 3 is afragmentary perspective showing the form of attachment ofFigs. l1 and 2 to a much enlarged scale; and Figs. 4, 5 and 6 are viewssimilar to Fig. 3, but showing other forms of apparatus embodying myinvention. v

In furnaces, particularly those in which powdered coa-l is burned, theincombustible solids carried by the heated gases tend to collect on theheat exchanging tubes of the furnace with which the heated gases contactor 'which are otherwise exposed thereto whenever the top surface of thetubes is in- 40 clined at an angle less than the angle of repose of thesolids, the solids tend to build' up on the top of the tubes andgradually extend around the tubes so as to form hard thick clinkerswhich may substantially protect the tubes from direct contact with theheated gases and in extreme cases may entirely bridge the space betweenadjacent tubes. Among the practical results of the accumulation of suchsolids is a loss of heat transfer toI W the Huid within the tubes and aserious decrease in the area of the tubes exposed to the radiant heat ofthe gases. By my invention I am enabled to prevent the accumulation ofsuch solids on the tops of heat exchange tubes in a furnace and to makethe tubes substantially self-cleaning. By means of various forms ofapparatus embodying my invention I am able also to provide desirableadditional strength and support and especially in a directionlongitudinally of the tubes.

In Fig. 1 I have shown fragmentarily a furnace of the powdered fuelburning type in which the flame is indicated at l, the side walls of thefurnace at 2, and the furnace bottom at 3 which is provided with an ashgate, not shown. A lorry car for carrying away ashes discharged from thefurnace bottom may be brought into loading position below this door.Heat exchange tubes 4 adapted to contain water are shown supported inthe opposite walls 2 and spanning the space therebetween where they areexposed to the heated gases and to incombustible solids carried by thegases. At either end of the tubes are shown headers 5 and 6communieating with the tube 4 and also with tubes 7 and 8 which leadWater to and from the headers 5 and 6, respectively. -The tubes 7 and 8preferably connect into the circulatory system of a water tube boiler 9.

It will be understood that incombustible solids such as ash, slag andthe like carried by the heated gases and the liame l will tend tocontact with the top of the tube 4 as they move downwardly under theinfluence of the iame and gas pressure and of gravity, and will lodgeand remain Aon the tubes 4 if the top surfaces of the tubes are inclinedat a lesser angle than the angle of repose of the solid materials. Inthe case of a round tube the surface thereof is relatively flat at thetop and such surface, even though relatively small, affords a lodgingplace for the solids. This is particularly true where the tubes are notlongitudinally inclined at an angle greater than the angle of repose ofthe solids, for example tubes 4, as shown herein.

Referring now more particularly to'Fig. 3 in which I have shown one formof apparatus embodying my invention, a tube assembly is shown in which4indicates the substantially round tube of the same number appearing inFigs. 1 and 2. This tube is provlded with an attachment extendinglongitudinally for substantially the entire length of the tube and intothe walls 2 where it may, in part at least, be supported, as by rbeingreceived in recesses 2a. This attachment as shown consists of aplurality of saddle members 10, each having a substantially semicircularsurface 11 conforming to the outer surface of the tube 4 with which theycontact, and yoke or covering members 12 securely held in close contactwith the outer surfaces of the saddle members 10. Saddle members 10 arepreferably extended above and below the tube 4 to permit the passagetherethrough of bolts or rlvets 13 which may be inserted and drawn uptightly against the members 12 while hot so as to result 1n closesurface engagement between the members 10 and 12 and the members 10 withthe tubes 4 when the attachment is at the temperature to which the tubeis ordinarily exposed. The saddle members 10 are preferably providedabove the top of tube 4 with one or more plates having surfaces 14inclined to the hori- 1 zontal at an angle greater than the angle ofrepose of the solids carried by the heated gases, and shown in thesefigures at an angle of approximately .y :Solid material coming incontact with these surfaces will not lodge thereon but will pass downbetween the tubes onto the furnace bottom 3. By reason of the closesurface contact of the members 12, 10 and 4, the effective heatingsurface of the tube 4 will be greatlyl increased and heat absorbed bythe members 12 and 10 will be readily .communicated to the tube 4.Moreover, the shape of the parts 10 and 12 and their assemblage as justdescribed will result in a very rigid structure, being in effect a beam'spanning the furnace, whic when supported at its ends by the walls 2 ofthe furnace, will not only be self-supporting, but will also strengthenand support the tube 4 longitudinally and also transversely and overcomethe/tendency of water tubes to buckle or sag as now frequently hap ens.

In the form of apparatus shown 1n Fig'. 4, the saddle members 10a havebeen made quite short and are spaced apart as shown. The covering 12a isof one continuous piece extending around both sides and the top of thesaddle members and clamped to these by any suitable means, such astheyrivets or bolts above referred to. In this case, heat -is receivedall along the covering 12a from the hot gases, and is conducted alongthe covering to the saddle membersand by these to the tube. Thev slopeof the upper sides of the covering is, of course, greater than the angleof repose of the ash and slag so that these drop olf, as in the formfirst described.

In Fig. 5, I have shown another form `of ap-l paratus embodying myinvention, this modification taking the form of an angular sheet the topthereof. Obviously, either one or two inclined surfaces per tube may beused and the angle thereof varied without departing from the spirit ofmy invention so long as the angularity is suflicient to accomplish thedesired purpose. The attachment 12b likewise strengthens the tubeslongitudinally and increases the effective area thereof exposed to theheated gases as it is attached to the tube by a good heat conductingconnection.

The form shown in Fig, 6 is very similar to that of Fig. 5, comprisingan angular sheet metal strip 120, welded or otherwise attached to a tube4c. In this form, however, one side of the angular strip is Vertical andthe other inclined at a greater angle than the angle of repose of solidmaterial, which may reach it and functions as do the two sloping sides othe preceding forms.

Having thus described my invention so that those skilled in the art maybe enabled to practice the same, I have defined its scope by what isclaimed, it being understood that variations, changes or modificationsmay bel made in the structure which has been hereinyabove described forpurposes of illustration only, and that such changes and modificationsre within thescope and spirit of my invenion.

What is claimed is:

1. A heat exchange tube for a furnace said tube adapted to bepositionedLin the path of heated gases carrying incombustible solids,and an attachment therefor comprising a plurality of saddlememberssubstantially sursounding the tube and extending lengthwisethereof and a yoke member having heat conductlng connections with thesaddle members, the said attachment havingsurfaces disposed' above thetop ofthe tube and inclined at an i angle greater than the angle ofrepose of the '120 said solids. l

2. A tube assembly for substantially horizontal disposition in a furnacecom rising a heat exchange tube, a deflector there or, spacing meansinterposed between the deflector repose of solid material carried bygases of*1 the furnace.

and tube at intervals, and means for securing 3. A tube assembly forsubstantially horizontal disposition in a furnace comprlsing a heatexchange tube, a deilector therefor, spacing means interposed betweenthe deflector and tube at intervals, and means for securing closesurface contact'between the deliector, spacing means and tube wherebythe heat absorbed by the deflector is readily communicated to the tube,the upper surface of the delector being disposed at an angle greaterthan the angle of re ose of solid material carried by gases of theurnace.

4. In combination with a powdered fuel burning furnace having acombustion chamber in which heated gases carrying incombustible residuesare forcibly directed downwardly, a plurality4 of heat exchange tubesextending across the lower portion of the chamber in the path of thedownward iow of gases and spaced apart from each other, a metalextension projecting upwardly from each tube and having heat conductingconnection therewith and provided with upper surfaces inclined at agreater angle than the angle of repose of ash and molten slag in thegases whereby the ash and molten slag will pass downwardly between thetubes without adhering thereto.

5. A wrought iron boiler tube of the char acter described having thereona separately formed cover of good heat-transmitting properties extendinglongitudinally of the tube substantially from end to end thereof andbeing substantially apicalin cross View, for the purposes specified.

6. A boiler tube of the character .described having attached on thenormally upper surface thereof a soot-deflectingstructure ex-i tendinglongitudinally of the tube substantially from end to end thereof andbeing substantially triangular in cross view, for the purposesspecified.

In testimony whereof I hereunto affix my signature this 24th day ofMarch, 1926.

- FRANK B. ALLEN.

